Related work.
In [1]}, the authors considered the single-source single-server and first-come-first-serve (FCFS) queue model and determined the arrival rate that minimizes AoI. A series of works afterwards investigated average AoI minimization under various system models with multiple sources, servers and different queue models. Different cases of multiple-source single-server under FCFS and last-come-first-serve (LCFS) were considered in [2]}, [3]} and the region of feasible age was derived. In [4]}, [5]}, the system is modeled as a source that submits status updates to a network of parallel and serial servers, respectively, for delivery to a monitor and AoI is evaluated. The parallel-server network is also studied in [6]} when the number of servers is 2 or infinite, and the average AoI for the FCFS queue model was derived. The authors in [7]} also
considered a system with multiple sources, where packets are sent to the parallel queues. They compute the average AoI of a system with only two parallel servers and compare the average AoI with the case of a single queue. In [8]}, the authors considered a model with multiple sources, a single queue and multiple destinations. A real time monitoring system where IoT devices have to transmit status updates to a common destination is considered in [9]}. The authors considered correlated status updates at the devices and showed that the optimal policy is threshold-based with respect to AoI at the destination.
